In recent years, a broadband communication line such as an ADSL which can send data at a high speed has been spread. The ADSL is characterized in that the same metallic cable as a telephone line is used as a subscriber's line, so that the same line can be used for both an analog telephone service and a network connecting service. That is, by inserting a filter called a splitter for dividing a frequency between the communication line and a communication terminal, the line can be separated into a line for sending a speech band signal and a line for sending digital data.
In the case of using the same line for the analog telephone service, although various constructions such as (ADSL modem+splitter+computer), (ADSL modem+splitter+router), . . . are possible as constructions of apparatuses of the subscribers, a construction in which, for example, portions of (ADSL modem+splitter) are integrated is possible as an ADSL gateway taking into consideration use as a telephone in common.
According to such an ADSL gateway, for example, a modular jack is provided so that an analog telephone can be connected to the line which sends a speech band signal and a communicating apparatus like a telephone or a facsimile is connected to the modular jack, thereby enabling communication to be made.
For the high-speed digital communication, a connecting interface of CSMA/CD (for example, Ethernet (trademark)) is provided for the ADSL gateway. By connecting a PC (personal computer) or the like to the CSMA/CD interface, data can be downloaded from the WWW server or the like at a high speed. Not only the CSMA/CD interface but also an interface such as a USB is used as an interface between the line and the network apparatus such as a PC.
Although a terminal such as a PC which is used to be connected to a server can make high-speed communication, a terminal such as telephone or facsimile for sending and receiving data in a real-time manner to/from an opponent terminal via a line exchange network (analog communication path) uses an analog band. While there are cases that do not become problems in an analog facsimile procedure of binary (black and white) image data or the like, there is a problem of requiring a long communication time in the case of sending color image (in a JPEG format or the like) data of a large capacity obtained by photographing an object with a digital camera or the like.
The high-speed transmission can be realized for sending communication data such as image data or the like at a high speed with such a procedure that the facsimile is connected to the CSMA/CD interface, the image data is uploaded as packets to a file server (for example, a protocol such as FTP, HTTP, or the like is used), and the opponent terminal downloads the image data from the server. In such a case, however, there is such a problem that since the reception side needs to execute the process to access to the server in order to receive the data, real-time performance of the communication is lost. In the case of notifying the server of a destination address of the receiving side or downloading the data on the initiation of the receiving side, a mechanism for notifying the receiving side of the uploading of the data, or the like is necessary. It is difficult to realize the communication with a simple operation of merely designating a telephone number of an opponent destination as in the conventional facsimile apparatus.
In consideration of the above problems, a technique for making image communication via servers on an IP network has been disclosed in Japanese Patent Application Laid-Open No. H10-107938 (the following Patent Document 1). That is, a first terminal of a sending side of an image calls the server in which the first terminal is included, the first terminal is connected to a computer network through the server in which the first terminal is included, and a second terminal serving as a receiving side of the image is designated, while a server of a network in which the second terminal calls the second terminal is included, the first terminal sends the image data to the server in which the second terminal is included through the computer network in a format suitable for the computer network, the server in which the second terminal is included converts the image data in the format adapted to the computer network into facsimile image data and sends it to the second terminal through a public line, and the second terminal reproduces the image from the facsimile image data.
Many methods of sending an image in an E-mail format by inputting an Internet address of a sending destination have been proposed in Japanese Patent Application Laid-Open No. H09-247334 (the following Patent Document 2), Japanese Patent Application Laid-Open No. H10-133967 (the following Patent Document 3), and the like.
Further, methods of relaying facsimile image transmission on the Internet in a real-time manner by applying the ITU-T Recommendation T.38 have been proposed in Japanese Patent Application Laid-Open No. 2000-354127 (the following Patent Document 4), Japanese Patent Application Laid-Open No. 2001-197279 (the following Patent Document 5), and the like.    [Patent Document 11] Japanese Patent Application Laid-Open No. H10-107938    [Patent Document 2] Japanese Patent Application Laid-Open No. H09-247334    [Patent Document 3] Japanese Patent Application Laid-Open No. H10-133967    [Patent Document 4] Japanese Patent Application Laid-Open No. 2000-354127    [Patent Document 5] Japanese Patent Application Laid-Open No. 2001-197279    [Patent Document 6] Japanese Patent Application Laid-Open No. H04-109736